Intramedullary Nail

ABSTRACT

An intramedullary device includes an intramedullary nail extending along a longitudinal axis from a proximal end to a distal end, a proximal portion of the intramedullary nail including a cavity extending from an opening at the proximal end along the longitudinal axis and a locking hole extending transversely therethrough along with a first insert sized and shaped for insertion into the cavity along the longitudinal axis thereof and including a transverse bore aligning with the locking hole.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/098,935 entitled “Intramedullary Nail” filed May 2, 2011, nowpending, which claims priority to and the benefit of U.S. ProvisionalApplication Ser. No. 61/362,937 filed on Jul. 9, 2010, entitled“Intramedullary Nail.” The disclosure of each application identifiedabove is incorporated herein by reference in its entirety for allpurposes.

TECHNICAL FIELD

The present disclosure generally relates to an intramedullary nail forfixation of fractured bones and more particularly to an intramedullarynail comprising an attachment structure for an insertion instrument andan insert for firmly securing locking screws to the intramedullary nail.

BACKGROUND

Intramedullary nails are commonly used as bone fixation devices forosteosynthesis purposes. Often these intramedullary nails featurelocking screws inserted transversely through the intramedullary nail foreither stabilizing the intramedullary nail in the bone or for fixationof individual bone fragments. These intramedullary nails may permitmultiple locking screws to be inserted therethrough at different anglesrelative to one another. The locking screws are often secured in theintramedullary nail via a plastic bushing or ring preventing the screwfrom migrating out of the intramedullary nail due to micro-motion orother loads. To secure these screws in the intramedullary nail, aninterference fit and a forced tapping of the screw into the bushing isgenerally applied. Other fixation features include metal interfaces thatmay be mechanically deformed and/or permit forced tapping in metal.These bushings should be formed of a material that is biocompatible.However, there is limited availability of such a material. One suchavailable plastic material is Ultra High Molecular Weight Poly-Ethylene(UHMWPE), which is a material that has been approved worldwide forimplantation. Although the biocompatibility of this material is ideal,the material is difficult to process with required accuracy usingconventional processing and molding techniques.

An example of a locking intramedullary nail including transverse lockingholes and an insert for securing the locking screws in these lockingholes is known from EP Patent No. B 0 306 709 DAUERER. This knownintramedullary nail comprises a proximal and a distal insert withtransverse bores having a diameter smaller than the outer diameter ofthe locking screws so as to secure the locking screws in the lockingholes of the intramedullary nail. The insert is slidably inserted intothe central cavity of the intramedullary nail. This known intramedullarynail, however, does not comprise an attachment structure at the proximalend to fix an insertion instrument to the nail.

One problem associated with the above described intramedullary nailsinvolves the attachment mechanism for an insertion handle or aimingdevice which is usually arranged at the proximal end of commonly usedintramedullary nails is that the insert must have a small outer diameterin order to be introduced through a central opening of the attachmentmechanism.

Thus, there remains a need for an improved intramedullary nail for arigid fixation between the nail and the bone including an attachmentmechanism for a surgical instrument and an insert, which permits thelocking screws to be firmly secured in the locking holes of theintramedullary nail

SUMMARY

The present disclosure relates to an intramedullary nail having anattachment mechanism for an insertion instrument and an insert withtransverse holes that are adapted and configured to firmly securelocking screws in the intramedullary nail.

According to the present disclosure, an intramedullary nail is extendingalong a longitudinal axis from a proximal end to a distal end, the nailcomprising a cavity extending from an opening at the proximal end alongthe longitudinal axis and a first locking hole extending transverselythrough the nail sized and shaped to receive a locking screwtherethrough along with a first insert sized and shaped for insertioninto the cavity including a first transverse bore arranged so that, whenthe insert is in the desired position within the cavity, the first boreis aligned with the first locking hole so that a locking screw insertedthrough the first locking hole passes through the insert via the firstbore and a second insert sized and shaped to be lockingly receivedwithin the cavity proximal of the insert to lock the insert at thedesired position in the cavity.

Some advantages of the intramedullary nail according to an embodiment ofinvention are that the insert does not have to be assembled through anattachment mechanism, e.g. an internal thread at the proximal end of theintramedullary nail, and can therefore have an increased diameter. Inaddition, due to the increased diameter, the insert can be manufacturedfrom ultra-high molecular weight polyethylene (UHMWPE) by usingconventional processing and molding techniques. Further, due to theincreased diameter of the insert, the locking screws can be firmlysecured in the transverse bores of the insert and consequently in thelocking holes of the intramedullary nail.

In one exemplary embodiment of the intramedullary nail, the first inserthas an outer diameter D and the central bore has an inner diameter d andwherein the outer diameter D is greater than the inner diameter d of thecentral bore of the second insert.

In a further exemplary embodiment of the intramedullary nail, the firstinsert is made of ultra-high molecular weight polyethylene (UHMWPE).Preferably, the second insert and the intramedullary nail are made ofTAN.

In another exemplary embodiment of the intramedullary nail, the firstinsert has an anti-rotation mechanism for preventing rotation of thefirst insert in the cavity in the intramedullary nail. Due to theanti-rotation mechanism the first insert is kept in a rotatively fixedposition relative to the intramedullary nail so that the transversebores in the first insert are aligned with the locking holes in theproximal part of the intramedullary nail.

In again another exemplary embodiment of the intramedullary nail, thefirst insert has more than one transverse bore.

In yet a further exemplary embodiment of the intramedullary nail, atleast two transverse bores in the first insert extend in differentdirections.

In still a further exemplary embodiment of the intramedullary nail thesecond insert is fixed in the cavity of the intramedullary nail by oneor more laser-welds. Preferably, the laser weld is a circumferentialweld. Alternatively, the laser-welds are two small longitudinallaser-welds. Additionally, the second insert can be fixed in the cavityin the intramedullary nail via an external thread or a press-fit.

In another exemplary embodiment, the first insert has a cylindricalshape.

According to a further aspect of the present disclosure, an assembly isprovided comprising an intramedullary nail and one or more lockingscrews, wherein the locking screws have a greater diameter than thetransverse bores in the first insert.

In accordance with another aspect of the present disclosure, a methodfor assembling the intramedullary nail according to the invention isprovided which comprises the steps of inserting a first insert into acavity of a intramedullary nail, the intramedullary extending along alongitudinal axis from a proximal end to a distal end and including afirst locking hole extending transversely through the nail sized andshaped to receive a locking screw therethrough, the cavity extendingfrom an opening at the proximal end along the longitudinal axis, theinsert including a first transverse bore arranged so that, when theinsert is in the desired position within the cavity, the first bore isaligned with the first locking and inserting a second insert into thecavity of the intramedullary nail, the second insert sized and shaped tobe lockingly received within the cavity proximal of the insert to lockthe insert at the desired position in the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present disclosure will be described in thefollowing by way of example and with reference to the accompanyingdrawings in which:

FIG. 1 illustrates a perspective exploded view of an exemplaryembodiment of the intramedullary nail according to the presentdisclosure;

FIG. 2 illustrates an exploded view in a longitudinal section of theembodiment of the intramedullary nail of FIG. 1;

FIG. 3 illustrates a longitudinal section of the embodiment of theintramedullary nail of FIG. 1 in the assembled state;

FIG. 4 illustrates a perspective view of the embodiment of theintramedullary nail of FIG. 1 in the assembled state; and

FIG. 5 illustrates a lateral exploded view of the embodiment of theintramedullary nail of FIG. 1.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure may be further understood with reference to thefollowing description and the appended drawings, wherein like elementsare referred to with the same reference numerals. The present disclosuregenerally relates to an intramedullary nail for fixation of fracturedbones and more particularly to an intramedullary nail comprising anattachment structure for an insertion instrument and an insert forfirmly securing locking screws to the intramedullary nail. It should benoted that the terms “proximal” and “distal” as used herein are intendedto refer to a direction toward (proximal) and away from (distal) a userof the intramedullary nail.

As shown in FIGS. 1 to 5, an intramedullary nail 1 extends along alongitudinal axis 11 from a proximal end 13 to a distal end and includesa cavity 14 extending through a proximal portion 12 thereof. Theintramedullary nail 1 further comprises a first insert 2 and a secondinsert 3 insertable through the cavity 14. The intramedullary nail 1includes the proximal portion 12 and a distal portion 9, the proximalportion 12 including the cavity 14 extending longitudinally therethroughand a plurality of locking holes 15 for receiving locking screwsextending transversely therethrough. The first insert 2 is inserted intothe cavity 14 and the second insert 3 is inserted into the cavity 14proximally of the first insert 2. The cavity 14 extends coaxially withthe longitudinal axis 11 and is open at the proximal end 13. The cavity14 may include an enlarged diameter portion at the proximal end 13including an internal thread 19 extending thereabout for engaging thesecond insert 3. Further, the cavity 14 may also include a contractionwhich forms an axial stop 16 to prevent the first insert 2 from movingdistally therepast toward the distal part 9 of the intramedullary nail1. The plurality of locking holes 15 extend through the proximal portion12 of the intramedullary nail 1 transversely to the longitudinal axis11. Each of the locking holes 15 have a hole axis 17 and are arranged insuch a manner that the hole axis 17 of each of the locking holes 15orthogonally cuts the longitudinal axis 11 of the intramedullary nail 1.Further, the locking holes 15 are spaced apart from each other along thelongitudinal axis 11 of the intramedullary nail 1. The locking holes 15are staggeredly arranged so that the hole axes 17 of the four lockingholes 15 extend at an angle relative to one other when viewed in across-section orthogonal to the longitudinal axis 11 of theintramedullary nail 1. In a preferred embodiment, the intramedullarynail 1 includes four locking holes 15. It will be understood by those ofskill in the art, however, that the intramedullary nail 1 may includeany number of locking holes 15.

The first insert 2 may have a cylindrical body 27 extending along acentral axis 24 from a proximal end 21 to a distal end 22. The firstinsert 2 includes an eccentric nose 25 at the distal end 22. The firstinsert 2 is coaxially positioned in the cavity 14 and includes aplurality of transverse bores 20 extending transversely therethrough,each of the transverse bores 20 having a bore axis 26. The transversebores 20 are arranged in such a manner that the bore axes 26 extendorthogonally of the central axis 24 and are equally spaced apart andextend at equal angles relative to each other, corresponding to aposition of the locking holes 15 in the proximal part 12 of theintramedullary nail 1. Thus, when inserted into the cavity 14, thetransverse bores 20 in the first insert 2 may be exactly aligned withthe locking holes 15 in the proximal part 12 of the intramedullary nail1.

As illustrated in FIG. 3, the eccentric nose 25 engages acomplementarily shaped eccentric portion 10 in the cavity 14 when thefirst insert 2 is inserted in the cavity 14. Thus, the eccentric nose 25and the eccentric portion 10 form an anti-rotation mechanism 6, whichprevents the first insert 2 from rotating relative to the cavity 14 inthe intramedullary nail 1. The cylindrical body 27 of the first insert 2may also include a stop face 23 proximally of the eccentric nose 25 forcontacting the axial stop 16 in the cavity 14 of the intramedullary nail1 when the first insert 2 is completely inserted in the cavity 14. Thesecond insert 3 may also be cylindrical, including a central bore 30.The second insert 3 is fixedly positioned in the cavity 14 coaxially andproximally of the first insert 2. The second insert 3 may have aninternal thread 31 along an inner surface of the central bore 30 and anexternal thread 32 along an outer surface thereof, which corresponds tothe internal thread 19 of the enlarged diameter portion of the cavity 14such that the second insert 3 may threadedly engage the cavity 14. Thecavity 14 also includes a shoulder 18 therein, which is distal of theenlarged portion so that the second insert 3 contacts the shoulder 18and is prevented from moving distally therepast, further into the cavity14.

The first insert 2 has been described as having an eccentric nose 25. Itwill be understood by those of skill in the art, however, that othernose configurations are also possible. For example, the nose could beconcentric but have a flattened edge to provide the anti-rotationmechanism with a complementarily shaped eccentric portion in a cavity.In another example, the nose could feature two or more complementaryedges that have rotational symmetry of, for example, order 2.

As illustrated in FIG. 2, a portion of the cavity 14 which receives thefirst insert 2 and which is axially limited by the axial stop 16 and bythe shoulder 18 has a length L which is slightly greater than a lengthl₂ of the cylindrical body 27 of the first insert 2. The central bore 30of the second insert 3 may act as a fixation structure for coupling aninsertion instrument such as, for example, an insertion handle and/or anaiming device, to the intramedullary nail 1. The first insert 2 has anouter diameter D and the central bore 30 has an inner diameter d,wherein the outer diameter D of the insert 2 is greater than the innerdiameter d of the central bore 30 of the second insert 3. Thus, once thefirst insert 2 is fully inserted in the cavity 14 it cannot be axiallydisplaced upon insertion of the second insert 3 but is retained by thesecond insert 3 in the cavity 14.

As illustrated in FIGS. 4 and 5, the second insert 3 is fixed in thecavity 14 of the intramedullary nail 1 via a longitudinal laser-weld 5,which may be positioned in an oblong opening 28, which extends through awall of the proximal portion 12 of the intramedullary nail 1. In oneexemplary embodiment, the intramedullary nail 1 includes twolongitudinal laser-welds 5 and two oblong openings 28 that are axiallylocated between the shoulder 18 in the cavity 14 and the proximal end 13of the intramedullary nail 1. Further, the two oblong openings 28 have along axis each which extends parallel to the longitudinal axis 11 of theintramedullary nail 1 and when viewed in a cross-section orthogonal tothe longitudinal axis 11 the two oblong openings 28 are arranged at anangle relative to one another. In another embodiment, the second insert3 may be welded, for example circumferentially, to the cavity 14 at theproximal end 13 of the intramedullary nail 1, between an exteriorsurface of the second insert 3 and an interior of the enlarged diameterportion at the proximal end 13 which receives the second insert 3.

Furthermore, the transverse bores 20 in the first insert 2 have asmaller diameter than the locking screws (not shown) used to lock theintramedullary nail 1 in a bone. Therefore, the thread of the lockingscrew cuts into the wall which limits the respective transverse bore 20so that the locking screws are secured against loosening within thetransverse bores 20 and consequently within the locking holes 15 of theintramedullary nail 1 so that a rigid fixation of the locking screws inthe intramedullary nail 1 can be achieved.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutions,and alterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present disclosure, processes, machines, manufacture,composition of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present disclosure.

It will be appreciated by those skilled in the art that variousmodifications and alterations of the invention can be made withoutdeparting from the broad scope of the appended claims. Some of thesehave been discussed above and others will be apparent to those skilledin the art.

1. A intramedullary bone fixation system comprising: an intramedullarynail having a proximal end, a distal end spaced from the proximal endalong a longitudinal axis, a cavity extending from the proximal end ofthe nail toward the distal end, and at least one locking hole thatextends through the nail along a locking hole axis that is substantiallytransverse to the longitudinal axis, the at least one locking holehaving a first cross-sectional dimension; and an insert in the nailcavity, the insert having a first end, a second end spaced from thefirst end along a longitudinal axis toward the distal end of the nail,and at least one bore that extends through the insert, wherein the atleast one bore is aligned with the at least one locking hole along thelocking hole axis, wherein the at least one bore defines a secondcross-sectional dimension that is less than the first cross-sectionaldimension.
 2. The intramedullary bone fixation system of claim 1,further comprising at least one locking screw configured for insertioninto the at least one locking hole and the least one bore, wherein theat least one locking screw has a threaded portion having a thirdcross-sectional dimension that is greater than the secondcross-sectional dimension.
 3. The intramedullary bone fixation system ofclaim 2, wherein the threaded portion of the at least one locking screwis configured to cut into the at least one bore when the threadedportion of the at least one locking screw is inserted into the at leastone bore.
 4. The intramedullary bone fixation system of claim 3, whereinthe insert is ultra-high molecular weight polyethylene.
 5. Theintramedullary bone fixation system of claim 4, wherein theintramedullary nail is metallic.
 6. The intramedullary bone fixationsystem of claim 1, wherein the intramedullary nail defines a stop in thecavity, and wherein the cavity includes a proximal cavity portion thatextends from the proximal end of the intramedullary nail to the stop,wherein the insert is disposed in at least a portion of the proximalcavity portion.
 7. The intramedullary bone fixation system of claim 6,wherein the second end of the insert defines a stop face that isadjacent to the stop in the cavity.
 8. The intramedullary bone fixationsystem of claim 7, wherein the insert has a projection that extends fromthe stop face toward the distal end of the intramedullary nail.
 9. Theintramedullary bone fixation system of claim 6, wherein the insert is afirst insert, wherein the bone fixation further comprises a secondinsert configured for insertion in the cavity adjacent to the firstinsert.
 10. The intramedullary bone fixation system of claim 9, whereinthe second insert includes an external thread on an outer surfacethereof, wherein the cavity defines an internal thread adjacent to theproximal end of the nail, wherein the external thread of the secondinsert is configured to engage the internal thread of the intramedullarynail.
 11. The intramedullary bone fixation system of claim 9, whereinthe cavity includes a shoulder disposed between the proximal end of theintramedullary nail and the stop, and the second insert is configured tocontact the first end of the first insert and the shoulder.
 12. Theintramedullary bone fixation system of claim 1, wherein the at least onelocking hole is a first locking hole and a second locking hole, andwherein the at least one bore is a first bore and a second bore, whereinthe first bore is aligned with the first locking hole and the secondbore is aligned with the second locking hole along respective lockinghole axes.
 13. The intramedullary bone fixation system of claim 12,wherein the first and second locking holes extend through theintramedullary nail at an angle relative to one another.
 14. Theintramedullary bone fixation system of claim 12, wherein the at leastone locking screw is a first locking screw and a second locking screw,wherein the first locking screw is configured for insertion into thefirst locking hole and the first bore, and the second locking screw isconfigured for insertion into the second locking and the second bore.15. A method for securing an intramedullary nail to a bone, the nailhaving a proximal end, a distal end spaced from the proximal end along alongitudinal axis, and a cavity extending from the proximal end towardthe distal end, the method comprising: inserting a locking screw throughat least one locking hole in the intramedullary nail, the at least onelocking hole extending along a locking hole axis that is substantiallytransverse to the longitudinal axis, wherein the locking screw has athreaded portion defining a first diameter; and causing the threadedportion of the locking screw to cut into the at least one bore definedby an insert, the at least one bore extending transversely through theinsert, and wherein the insert is disposed in the cavity such the atleast one bore is aligned with the at least one locking hole, whereinthe at least one bore has a second diameter that is less than firstdiameter.
 16. The method of claim 15, wherein the at least one lockinghole is a first locking hole and second locking hole, and the at leastone bore is a first bore and a second bore, and the locking screw is afirst locking screw, wherein the method further comprises the steps of:inserting a second locking screw into the second locking hole; andcausing a threaded portion of the second locking screw to cut into thesecond bore.
 17. The method of claim 15, wherein the step of insertingthe locking screw includes the step of inserting the locking screw in atleast one locking hole that is disposed at a proximal portion of theintramedullary nail, the proximal portion being adjacent to the proximalend of the intramedullary nail.
 18. The method of claim 15, furthercomprising advancing the threaded portion of the locking screw throughthe at least one locking hole and the at least one bore so as to engagethe bone.
 19. The method of claim 15, wherein the insert is a firstinsert, wherein the method further comprises the step of inserting asecond insert through an opening at the proximal end of the nail intothe cavity proximal to the first insert.
 20. The method of claim 19,wherein the step of inserting the second insert further comprisesadvancing the second insert into the cavity along the longitudinal axisinto contact with a shoulder defined by the cavity and a proximal end ofthe first insert.